Split-Gate Trench MOS Transistor Body Self-Alignment

Solution Overview

Problem

The misalignment between the body region and gate regions in MOS transistors due to etching variations in the formation of insulating layers leads to increased gate/drain capacitance and drain/source on-state resistance, adversely affecting the switching frequency and Safe Operating Area (SOA) of the MOS transistor.

Innovation Solution

A self-alignment process is employed by implanting dopants along tilted directions to form the body region, ensuring it aligns in depth with the gate regions, using a combination of silicon oxide and silicon nitride layers to control the implantation path and achieve precise alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional etching process is used to form insulating layers, then manufacturing process is simple, but misalignment between body region and gate regions occurs leading to increased gate/drain capacitance and drain/source on-state resistance

Engineering Contradiction:

Improvealignment precision between body region and gate regionsVSAvoidcomplexity of manufacturing process

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by forming the body region first through tilted dopant implantation before forming the gate regions. This sequence ensures that the body region is already in place at the correct depth and orientation, allowing subsequent gate formation to automatically align with it. The tilted implantation angle (e.g., 45 degrees) is specifically chosen to ensure the body region forms at the precise depth where gate regions will later be positioned, eliminating alignment issues that would otherwise require complex etching processes.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If tilted dopant implantation is used to form body region, then alignment with gate regions is improved, but manufacturing process complexity increases

Engineering Contradiction:

Improvealignment precision between body region and gate regionsVSAvoidease of manufacturing process

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent applies self-service by using the tilted dopant implantation process to automatically self-align the body region with the subsequently formed gate regions. The tilted angle of implantation causes the dopants to reach a specific depth that corresponds exactly to where the gate regions will be formed, without requiring additional alignment steps or complex etching processes. The process serves itself by using the implantation geometry to inherently define the alignment, eliminating the need for separate alignment procedures.

Inventive Principle:

Principle #25Self-service

3Ease of manufacture

If misalignment between body region and gate regions occurs, then manufacturing is easier, but gate/drain capacitance and drain/source on-state resistance increase

Engineering Contradiction:

Improveease of manufacturing processVSAvoidelectrical performance of MOS transistor

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies preliminary action by forming the body region first through tilted dopant implantation before forming the gate regions. This sequence ensures that the body region is already in place at the correct depth and orientation, allowing subsequent gate formation to automatically align with it. The tilted implantation angle (e.g., 45 degrees) is specifically chosen to ensure the body region forms at the precise depth where gate regions will later be positioned, eliminating alignment issues that would otherwise require complex etching processes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies self-service by using the tilted dopant implantation process to automatically self-align the body region with the subsequently formed gate regions. The tilted angle of implantation causes the dopants to reach a specific depth that corresponds exactly to where the gate regions will be formed, without requiring additional alignment steps or complex etching processes. The process serves itself by using the implantation geometry to inherently define the alignment, eliminating the need for separate alignment procedures.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This alignment reduces variations in gate/drain capacitance and drain/source on-state resistance, enhancing the switching frequency and SOA of the MOS transistor.

Implementation Method 1

implanting dopants along one or more implantation directions that are tilted with respect to a front surface of the die

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Data Source

PatentUS12389620B2Split-gate trench MOS transistor with self-alignment of gate and body regions

Publication Date: 2025.08.12 STMICROELECTRONICS SRL

AI summary

A process is proposed for manufacturing an integrated device having at least one MOS transistor integrated on a die of semiconductor material. The process includes forming one or more gate trenches with corresponding field plates and gate regions. A body region is formed by implanting dopants selectively along one or more implantation directions that are tilted with respect to a front surface of the die. Moreover, a corresponding integrated device and a system comprising this integrated device are proposed.